The invention relates to all those applications in which a common secret needs to be securely stored, but whereby compensation nevertheless needs to be effected in a secure manner in the event of loss of the secret. With regard to the secret, this can for example be a password. Resetting of the password in the event of a lost password should not be permitted.
Within the scope of the automation of industrial systems in particular this can relate to a project password or to the protection of know-how (concerning software modules for a stored program controller, for example). In this situation, the object to be protected can likewise be secured by means of a password.
Furthermore, within the scope of FDA there is frequently a requirement for passwords to be stored not openly but by being dealt with cryptographically. The difficulty with the retrieval of the secret or of the password thus also presents itself in this environment.
In general, the invention thus relates to systems which store a password in a cryptographically secure form (the hash value of a password, for example). These systems are as a rule not in a position to be able to output the password if the user has forgotten the password.